Antrodiaetidae, also known as folding trapdoor spiders or folding-door spiders, is a small spider family related to atypical tarantulas. They are found almost exclusively in the western and midwestern United States, from California to Washington and east to the Appalachian mountains. Exceptions include Antrodiaetus roretzi and Antrodiaetus yesoensis, which are endemic to Japan and are considered relict species. It is likely that two separate vicariance events led to the evolution of these two species. Genera , the World Spider Catalog accepted the following genera: Aliatypus Smith, 1908 — United States Antrodiaetus Ausserer, 1871 — United States, Japan Atypoides O. Pickard-Cambridge, 1883 — United States Hexura Simon, 1884 — United States Name The name “folding-door” describes how they open or close the entrance to their burrow; they unfold or fold the door. See also List of Antrodiaetidae species References Hendrixson, B.E. & Bond, J.E. (2005). Two sympatric species of Antrodiaetus from southwestern North Carolina (Araneae, Mygalomorphae, Antrodiaetidae). Zootaxa 872:1-19. PDF (A. unicolor, A. microunicolor) External links Images of a folding trapdoor spider Mygalomorphae families Taxa named by Willis J. Gertsch